Magnetic gasket suitable for forming a seal between a fixed part and an openable part

ABSTRACT

This invention relates to a magnetic gasket particularly suitable for forming a seal between a fixed part and an openable part including in regions of curvilinear extension, for example between the body and door of a vehicle, of the type comprising an element for fixing to one of said parts and a seat housing a magnetized bar (11) of substantially rectangular cross-section in which said fixing element and said seat (8) for the magnetized bar are connected together by an extendable deformable tubular chamber, characterised in that said bar (11) is magnetized along at least one of the two shorter opposing sides (19, 19&#39;) of its substantially rectangular cross-section, said magnetized side facing when in its operating position the part with which contact is to be made for sealing purposes.

BACKGROUND

Gaskets for motor vehicles are known, for example from Italian PatentNo. 1,017,502 and Italian Utility Model No. 21692 8/83 in the name ofthe present applicant, which are suitable for forming a seal between thevehicle body and openable parts of the bodywork, such as doors, hatches,hood and the like when these are closed, of the type comprising adeformable profiled strip able to be fixed to the vehicle body bysnapping-on, to said profiled strip there being connected along thestraight regions of engagement between the vehicle body and the openablepart a tubular section divided into a pair of separate adjacentchambers, one of which acts as a bellows air chamber and the other as aseat for magnetized material.

These magnetic gaskets represent considerable progress overcompression-operated gaskets without a magnetic seal, in terms both ofimproved sealing and of lesser pulling action to effect closure.

There is however the technical problem of adapting this type of gasketto the varying range of shapes which the engagement region between thefixed and openable parts can assume, particularly in curvilinearregions, and especially when the radius of curvature is small. In veryaccentuated curvature regions there are considerable problems relatingto deformation and squashing of the magnetic gaskets, which can resultin loss of seal, formation of folds and points of discontinuity, orindeed breakage of the gasket after a certain time.

European Patent Application No. 0519565 of the present applicantproposes a gasket able to solve this technical problem. It provides amagnetic gasket for forming a seal between a fixed part and an openablepart in regions of curvilinear extension, for example in particularbetween the body and door of a vehicle, of the type comprising aprofiled strip for fixing to said parts and a chamber housing amagnetized bar, in which said profiled fixing strip and said tubularchamber for the magnetized bar are connected together by an extendabledeformable tubular chamber the opposing free walls of which aresubstantially curvilinear and curved in the same direction.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a magnetic gasketideally suitable for mounting in curvilinear regions even of very smallradius of curvature, without the deformation stresses to which it issubjected in any way compromising the seal.

A further object is to provide the gasket with a continuous flexiblemagnetic bar to enable it to be shaped as a frame weldable at a singlepoint without other weld points being required. This means that therequired gasket can avoid the presence of weak points such as the weldedones more easily subjected to a potential loss of seal, infiltration,wear, breakage etc.

Further objects are to provide a gasket which can easily bend along oneaxis and vary its plane along the other axis, ensures good thermalinsulation (and acoustic insulation in the case of motor vehicles), canbe easily fitted to the parts, is of the lowest possible weight, and isable to "close" and hence exert magnetic force on possible narrowsurfaces (3-5 mm in the case of motor vehicles).

These objects are attained according to the invention by a magneticgasket particularly suitable for forming a seal between a fixed part andan openable part in regions of curvilinear extension, for example inparticular between the body and door of a vehicle, of the typecomprising an element for fixing to said parts and a seat housing amagnetized bar of substantially rectangular cross-section in which saidfixing element and said seat for the magnetized bar are connectedtogether by an extendable deformable tubular chamber, characterised inthat said bar is magnetized along at least one of the two shorteropposing sides of its substantially rectangular cross-section, saidmagnetized side facing when in its operating position the part withwhich contact is to be made for sealing purposes.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and advantages of the invention will be moreapparent from the description of some non-limiting embodiments thereof,given hereinafter with reference to the figures of the accompanyingdrawings.

FIG. 1 is a cross-section through a gasket according to the invention.

FIG. 2 is a sectional perspective view of a further embodiment of thegasket according to the invention.

FIGS. 3, 4, 5 and 6 are schematic views relative to the magnetization ofa bar suitable for the purposes of the invention.

FIG. 7 shows the gasket of FIG. 1 operationally mounted on a motorvehicle.

FIGS. 8 and 9 are cross-sections through two further embodiments of thegasket according to the invention.

DETAILED DESCRIPTION

With reference to the drawings, FIGS. 1, 2 and 7 show a gasket suitablefor use on a vehicle, for example for sealing between the vehicle bodyand openable parts such as doors, boot or hood. With reference to FIG.7, along a frame 1 of a motor vehicle body cooperating with an accessdoor 3 there is fixed a snap-on fixing element 4 with a metal core 5 andhaving a C-shaped cross-section. The element 4 is basically a ring fixedalong the entire extension of the frame 1, on which it is forced andsecured by the pressure exerted by the metal core, adherence beingcompleted by the action of soft saw-tooth projections 6 which act on thesurface of the vehicle body frame. Along the angular and curvilinearregions of the frame 1 the element 4 follows the shape because of itscapacity to deform and to assume a torus development.

On the opposite side to the snap-on element 4 there extends in thedirection of the door 3 a tubular seat 8 for a bar 11 of magnetizedmaterial, such as a plastoferrite bar, able to act as a magnetic poleagainst a counter-pole formed by the door 3 itself if this is offerromagnetic material, or by a suitable ferromagnetic plate 9 or amagnetic counter-pole located on the door in a position facing the bar11, if the door is for example of a magnetic material.

The magnetic bar 11 is of rectangular cross-section with opposing pairsof long sides 18, 18' and short sides 19, 19'.

According to the objects of the invention, as will be clarifiedhereinafter, the magnetic contact with the counter-pole is to beachieved on the short side 19 of the rectangular cross-section, on whichthe magnetic flux is therefore concentrated as can be seen in FIG. 4.

Consequently the rectangular cross-section of the seat 8 for themagnetic insert has its long sides substantially normal to the surfaceof the door 3 against which the magnetic bar engages for sealing.

With particular reference to FIGS. 1 and 7, the snap-on element 4 andthe seat 8 containing the magnetic bar 11 are connected together by aninterposed tubular chamber 10, which is elastically extendable anddeformable so that it can act as a bellows to enable the magnetic pole11 to adapt to the counter-pole 9 in every sealing region. Theconfiguration of the chamber 10 when viewed in cross-section is asfollows: the two opposing walls 12 and 13 are of essentially curvilinearand parallel extension, in the sense defined hereinafter. The wall 12 isthat which faces the vehicle body frame 1 and is hence that which is onthe outside when operationally mounted.

The wall 13 is that which is on the inside when in the operatingposition. The two walls 12 and 13 are therefore both curved towards theoutside of the shape which the gasket assumes within the curvilinearengagement region. The wall 13 is most curvilinear in its centralregion, whereas in its side portions 14 and 15 connected respectively tothe snap-on element and to the magnetic bar it is of rectilinearextension. From the rectilinear portion 14 there extends a rib 16 whichacts as a spacer between said two portions.

From the outer wall 12 there extends a corresponding spacer 17 in thedirection of the vehicle body frame 1. The bellows chamber 10 bothprovides thermal and acoustic insulation (in applications in which thisis required) and acts as an extendable connection element between thesnap-on element and the part against which the seal is to be effected.In this respect, to allow the magnetic bar effecting the seal to undergothe appropriate movements, the chamber preferably has the cross-sectionshown for example in FIG. 1, in which the inner wall 13 is connected tothe short side 19' of the magnetic insert 11 via the base 15 and thevertical wall 26' of the seat 8.

The outer wall 12 of the chamber 10 is connected to the short side 19 ofthe insert 11 via the opposite vertical wall 26 of the seat 8.

The chamber 10 is hence substantially of C cross-section, even if ofsuitably irregular shape determined by the specific sealingrequirements, which vary from case to case.

For example, in the gasket of FIG. 2, the inner wall 13 of the chamber10 is connected directly to the respective short side 19' (rather thanby way of the base 15 and vertical wall 26' of FIG. 1). In this case thecross-section of 10 assumes the form of a regular C.

The invention also relates to a process for magnetizing a bar, such assaid plastoferrite bar, to act as a magnet in the aforesaid gasket, andto the thus magnetized bar.

To magnetize a bar 11 of magnetizable material, such as plastoferrite,along the short sides 19 and 19' of its rectangular cross-section, it ispassed through the magnetic field generated by a pair of opposing north(N) and south (S) poles in the position shown in FIG. 3. In this manner,the short sides 19 and 19' of the bar 11 are arranged in a directionparallel to the axis 22 of the N-S magnet. By the effect of this type ofmagnetization, the bar 11 to act as the insert for the magnet has thelines of force 23 concentrated on said sides, as shown in FIG. 4.

FIGS. 5 and 6 show modifications to the described magnetization process,in which pairs of screening plates 20--20' or 21--21' are positionedalong the long sides 18--18' of the bar 11. FIG. 5 shows a pair ofplates aligned with the sides 18, 18', so that the lines of polarizationforce have the pattern indicated by 24. In FIG. 6 the pair of plates 21,21' is dimensioned to project beyond the sides 18, 18', so that thelines of magnetic polarization force are as indicated by 25.

In both cases, as the polarization is concentrated in the regionsinvolving the lines of force and hence no longer partly dispersed alongthe long sides of the cross-section, the magnetic attraction force isgreater than the case shown in FIG. 4.

FIG. 1 shows the use of a magnetic insert 11 provided with plates 20,20' in accordance with the magnetization process of FIG. 5. These platesare retained in position by the magnetic attraction force of the insert11, and have their edges suitably bevelled so that there is no danger ofdamaging the walls of the seat 8.

In addition, these plates can be suitably slotted to form points forrelieving the flexure to which they are subjected when the gasket is notmounted in a single plane but instead on concave or convex surfaces.

In a different embodiment, instead of the screening plates a compoundcontaining ferromagnetic material can be used, to be coextruded with theinsert 11 along the surface of the long sides 20, 20'. By this means acoextruded magnetic bar is formed having its central part of aferrite-containing compound and the lateral surfaces of the sides 20,20' of a compound containing ferromagnetic material (such as magneticsteel filings) the function of which is equivalent to that of thescreening plates. According to the present invention, the bar exhibitsits magnetic attraction force along the shorter side. This magneticattraction along the shorter side of its rectangular cross-section meansthat the gasket can undergo bending along its axis without problems,even in the case of small radii of curvature. This feature basicallyenables the magnetic bar to be used in the closure position or thenarrow side of the cross-section. The thickness of the magnetic inserton this side can be indicatively 2-4 mm, so that closure can take placeagainst narrow surfaces.

This magnetization differs substantially from that of magnetic gasketsof known type.

In this respect, for these latter an isotropic bar (ie having theferrite particles dispersed disorderedly within a polymer matrix) ismagnetized by 2 or 3 poles along the longer sides of its rectangularcross-section.

The method of the invention used to magnetize the plastoferrite bar toachieve an attraction force concentrated on the short side consistsbasically of axial magnetization parallel to the surface of contact,achieved by magnetization with opposing N-S poles as shown in FIG. 3,instead of side-by-side poles on one side of the bar.

For equal compounds and magnetization, the attraction force increaseswith the use of anisotropic magnetic bars, with particles orientatedparallel to the lines of flux of the magnetizer. This orientation can beobtained either by treating the compound or by orientation under amagnetic field during extrusion.

By way of example, in the practical application of the present inventionthe following values can be considered:

The orders of magnitude for a magnetic bar with a cross-section of 9.8mm×2.9 mm are as follows (attraction force measured on the 2.9 mm sidewith a magnetic gap of 0.45 mm).

isotropic bar with axial magnetization parallel to the surface ofcontact 2-10 g/cm

isotropic bar with axial magnetization parallel to the surface ofcontact (with screening plates) 5-20 g/cm

anisotropic bar with axial magnetization parallel to the surface ofcontact 15-30 g/cm

anisotropic bar with axial magnetization parallel to the surface ofcontact (with screening plates) 30-60 g/cm.

To obtain high attraction forces in another manner, composite ferriteswith rare earths or other suitable components can be used, however atconsiderably higher cost.

The attraction force of the magnetic bar has to satisfy determinedrequirements, bearing in mind the magnetic gap of thermoplastic rubberand remembering that in the case of motor vehicles an appropriate devicemay be provided to facilitate the opening of the doors.

Having fixed the radius of curvature, the maximum allowable thickness ofthe bar is calculated. On the basis of the required attraction force theheight of the bar is determined and also whether it is necessary to usescreening plates. For a low attraction force it may be sufficient forthe rectangular magnetic insert, as a borderline case, to be of a shapewhich is nearly a square. In this regard it is made clearthat--according to the purposes of the prevent invention--the term"rectangular cross-section" can also include, as a borderline case, asubstantially square cross-section or a cross-section in which the majorside is only slightly longer than the minor side.

On a square door of side measuring one meter, using a magnetic insertwith an attraction force of 50 g/cm and applying the force at 0.8 m fromthe hinge there is an opening-resistant couple of 12.5 kg:

    F=50×100=5000 g/side=5 kg/side

    M=5 (1+0.5+0.5)=10 kg

    Fo=10/0.8=12.5 kg

Although this provides safety against accidental opening of the doorduring running, it must not create opening problems when at rest.Because of this it may be necessary to provide a special mechanism tofacilitate door opening.

In all cases, optimum extendibility is obtained with the gasket of theinvention in a direction perpendicular to the surface of contact withthe counter-pole. This extendibility enables the gasket to operatecorrectly at all points, to take up any planarity differences in thesurface of contact and to ensure a seal along the entire outline betweenthe fixed part and the openable part.

For applications relating to refrigerator, freezer and similar doors anddoor liners, and to windows, door frames, cabins etc., the gasket cantake the form of that shown in FIGS. 8 and 9, which show thecross-section through a monoextruded gasket of soft elastic materialsuch as plasticized PVC, thermoplastic rubber or a traditionalvulcanized elastomer housing a magnetic bar 11 according to theinvention.

The bar 11 is provided with a pair of short sides 19 and 19' and a pairof long sides 18 and 18'.

The sides on which the lines of flux are concentrated are according tothe invention the pair of short sides 19 and 19', of which the sideintended to engage the fixed part on closure is the short side 19.

In this case the fixing element is a coupling base 27 in the case ofFIG. 8 or a pointed foot 28 for insertion into the recess in therefrigerator door liner or in the door or window frame.

FIG. 8 shows an example of a coextruded gasket in which the couplingfoot 27 can consist of a soft or rigid section, with soft material beingused for the rest of the gasket. The combination of rigid and softmaterial can be in the form of known two-hardness vulcanized elastomers,rigid and soft PVC, or coextrudable thermoplastic rubber and rigidmaterial, hence achieving perfect adhesion between rigid and softmaterials (such as thermoplastic olefin rubber and polypropylene, ABSand thermoplastic styrene or polyester rubber).

In both the cases shown in FIGS. 8 and 9, the extendable tubular chamber10 has the characteristic structure described for the precedingexamples. The operation of the gasket of the invention is henceessentially as already described.

In FIGS. 8 and 9 the extendable tubular chamber 10 has a lower region ofgreater thickness connected at a hinge point to an upper region oflesser thickness, to achieve a lateral stability effect as described inEuropean patent 155 016 of the present applicant. In the examplesillustrated in FIGS. 8 and 9 there is also provided a rib 29 which sealsagainst the door liner in the case of application to a refrigerator.

In the embodiments of FIGS. 8 and 9, screening plates can also beapplied as in the preceding examples to concentrate the magnetic forceon the short sides and prevent its partial dispersion along the longsides.

The gasket of the present invention can also be analogously applied todoor and window frames, verandas or general closures in the buildingindustry when adaptation to a certain curvature of the closure edge isrequired, for example in the case of doors or windows which are notperfectly rectangular but instead have a circular upper finish. In thesecases the parallel curved-wall shape of the bellows provides thenecessary curvature to the extruded section. This concept is applicablefor example to the magnetic gaskets described in Italian utility modelNos. 202.759 and 207.429 of the present applicant.

In addition, in the described fields of application the facility forfollowing curvatures gives the stylist considerable freedom in designingthe finished object, which would otherwise be dependent upon 90° orother angle welds.

Generally, from the aforegoing it will be apparent that the gasketaccording to the invention provides in an ideal manner the advantages ofbeing bendable and flexible along any outline shape along which a sealis required, even with small radii of curvature and without undergoingdeformation such as to compromise the seal. The continuity of the systemformed by the magnetic gasket without any interruption in the cornersdue to welding is also important according to the present invention, theresult being a considerably improved seal against cold and airinfiltration. The magnetic gasket according to the invention can undergonumerous modifications with respect to the aforegoing. What is essentialis to follow the basic concept of providing a magnetic bar along thesealing region in which that side of the bar which implements the sealis the side represented by the short side of the substantiallyrectangular cross-section of the bar. With regard to the manufacture ofthe magnetic gasket according to the invention, the normal methods forthis type of gasket can be used. For example, the extendable chambertogether with the seat for the magnetic bar and the fixing element, iethe snap-on element in the case of motor vehicles, can be formedtogether in coextruded material.

Alternatively, the snap-on element can be formed separately and bebonded to the extendable tubular connection chamber during extrusion.

We claim:
 1. A magnetic gasket suitable for forming a seal between afixed part and a moveable part in regions of curvilinear extension ofsaid parts, comprising:an element for fixing to one of said parts; and aseat housing a magnetized bar of substantially rectangularcross-section, said fixing element and said seat being connectedtogether by an extendable deformable tubular chamber, wherein said baris magnetized along at least one of two shorter opposing sides of itssubstantially rectangular cross-section, said magnetized side facing,when in its operating position, the other of said parts with whichcontact is made for sealing purposes, and wherein said extendabledeformable tubular chamber has opposing free walls which aresubstantially curvilinear and curved in the same direction, thusachieving a substantially C-shaped cross-section.
 2. A magnetic gasketas claimed in claim 1, wherein one of said walls of said extendabledeformable tubular chamber which, when in its operating position, facesinwards of the curvature of an engagement region between the fixed partand the movable part is essentially curved in a central part thereof,lateral portions thereof being of rectilinear extension.
 3. A magneticgasket as claimed in claim 1, characterised wherein said seat for themagnetic bar is formed within said C-shaped cross-section of theextendable tubular chamber.
 4. A magnetic gasket as claimed in claim 1,characterised wherein said seat for the magnetic bar is formed outsidesaid C-shaped cross-section of the extendable tubular chamber.
 5. Amagnetic gasket as claimed in claim 2, wherein said seat for themagnetic bar is formed along one of said lateral portions of rectilinearextension of said one wall of the extendable tubular chamber which facesinwards of the curvature.
 6. A magnetic gasket as claimed in claim 1,wherein at least said wall of said extendable chamber which faces thefixed part, is provided with a spacer.
 7. A magnetic gasket as claimedin claim 1, wherein said fixing element, said chamber for the magneticbar and said extendable chamber are separate parts, and are joinedtogether by a suitable means.
 8. A magnetic gasket as claimed in claim1, wherein said fixing element, a chamber for the magnetic bar and saidextendable deformable tubular chamber are made in one piece by one ofmolding and co-extrusion.
 9. A magnetic gasket as claimed in claim 1,wherein a screening layer for the magnetic force is applied along atleast one of the longer sides of the substantially rectangularcross-section of the magnetized bar.
 10. A magnetic gasket as claimed inclaim 9, wherein said at least one screening layer comprises metalplate.
 11. A magnetic gasket as claimed in claim 9, wherein said atleast one screening layer comprises ferromagnetic material coextrudedwith said bar.
 12. A magnetic gasket as claimed in claim 1, wherein inthe substantially rectangular cross-section of said magnetized bar, thelength of one pair of opposing sides is slightly greater than the lengthof the other pair of sides.
 13. A vehicle comprising:a magnetic gasketsuitable for forming a seal between a fixed part and a moveable part inregions of curvilinear extension, of said parts, said magnetic gasketincluding:an element for fixing to one of said parts; and a seat housinga magnetized bar of substantially rectangular cross-section, said fixingelement and said seat being connected together by an extendabledeformable tubular chamber, wherein said bar is magnetized along atleast one of two shorter opposing sides of its substantially rectangularcross-section, said magnetized side facing, when in its operatingposition, the other of said parts with which contact is made for sealingpurposes, and wherein said extendable deformable tubular chamber hasopposing free walls which are substantially curvilinear and curved inthe same direction, thus achieving a substantially C-shapedcross-section.
 14. A magnetic gasket suitable for forming a seal betweena fixed part and a moveable part in regions of curvilinear extension ofsaid parts, comprising:an element for fixing to one of said parts; and aseat housing a magnetized bar of substantially rectangularcross-section, said fixing element and said seat being connectedtogether by an extendable deformable tubular chamber, wherein said baris magnetized along at least one of two shorter opposing sides of itssubstantially rectangular cross-section, said magnetized side facing,when in its operating position, the other of said parts with whichcontact is made for sealing purposes, wherein said extendable deformabletubular chamber has opposing free walls which are substantiallycurvilinear and curved in the same direction, thus achieving asubstantially C-shaped cross-section, wherein one of said walls of saidextendable deformable tubular chamber which, when in its operatingposition, faces inwards of the curvature of an engagement region betweenthe fixed part and the movable part is essentially curved in a centralpart thereof, lateral portions thereof being of rectilinear extension,and wherein a spacer extends from at least one of said lateral portionstowards the other.